feat: add a hub for the client's own pages and gate mews:do action links

app/lib/application/pages/settings_page.dart

@@ -0,0 +1,100 @@
+import '../../l10n/strings.dart';
+import '../../mews/document.dart';
+import '../controllers/reader_settings_controller.dart'
+    show ReaderSettingsController;
+import 'mews_urls.dart';
+import 'page_blocks.dart';
+
+/// The bundled typefaces the reader can pick. Adding a font is one TTF in
+/// assets/fonts, one entry in pubspec.yaml, one entry here and one label in
+/// the locale file.
+const _fonts = <({String family, String labelId})>[
+  (family: 'Atkinson Hyperlegible', labelId: 'settings-font-atkinson'),
+];
+
+/// Message ids for the values the controller accepts. Kept literal so every
+/// id in the locale file can be found by searching for it.
+const _themeLabels = {
+  'light': 'settings-theme-light',
+  'dark': 'settings-theme-dark',
+  'system': 'settings-theme-system',
+};
+
+const _variantLabels = {
+  'site': 'settings-variant-site',
+  'warm': 'settings-variant-warm',
+  'cool': 'settings-variant-cool',
+  'green': 'settings-variant-green',
+  'mono': 'settings-variant-mono',
+};
+
+Future<MewsPage> buildSettingsPage(
+  Uri url, {
+  required ReaderSettingsController settings,
+  required Strings strings,
+}) async {
+  final title = strings.t('settings-page-title');
+  final scale = settings.fontScale.value;
+
+  return internalPage(
+    url: url,
+    title: title,
+    body: [
+      ...chrome(title: title, current: url, strings: strings),
+      HeadingBlock(2, [MewsText(strings.t('settings-font-heading'))]),
+      choiceRow([
+        for (final font in _fonts)
+          (
+            href: MewsUrls.action('set-font', {'value': font.family}),
+            label: strings.t(font.labelId),
+            current: font.family == settings.font.value,
+          ),
+      ]),
+      // Text size steps between the controller's bounds, with the current
+      // value between the two steps.
+      HeadingBlock(2, [MewsText(strings.t('settings-size-heading'))]),
+      itemList([
+        if (scale > ReaderSettingsController.minScale)
+          MewsListItem([
+            ParagraphBlock([
+              MewsLink(MewsUrls.action('set-size', {'step': 'down'}),
+                  [MewsText(strings.t('settings-size-decrease'))]),
+            ]),
+          ]),
+        MewsListItem([
+          ParagraphBlock([
+            MewsEmphasis(EmphasisStyle.strong, [
+              MewsText(strings.t('settings-size-value',
+                  {'percent': (scale * 100).round()})),
+            ]),
+          ]),
+        ]),
+        if (scale < ReaderSettingsController.maxScale)
+          MewsListItem([
+            ParagraphBlock([
+              MewsLink(MewsUrls.action('set-size', {'step': 'up'}),
+                  [MewsText(strings.t('settings-size-increase'))]),
+            ]),
+          ]),
+      ]),
+      HeadingBlock(2, [MewsText(strings.t('settings-theme-heading'))]),
+      choiceRow([
+        for (final mode in ReaderSettingsController.themeModes)
+          (
+            href: MewsUrls.action('set-theme', {'value': mode}),
+            label: strings.t(_themeLabels[mode]!),
+            current: mode == settings.themeMode.value,
+          ),
+      ]),
+      HeadingBlock(2, [MewsText(strings.t('settings-variant-heading'))]),
+      choiceRow([
+        for (final variant in ReaderSettingsController.variants)
+          (
+            href: MewsUrls.action('set-colors', {'value': variant}),
+            label: strings.t(_variantLabels[variant]!),
+            current: variant == settings.variant.value,
+          ),
+      ]),
+    ],
+  );
+}